Make fallback routes use InflectedRoute.

This preserves behavior with the old default routes, and since we don't
have :controller as a default key, this solves needing to re-add
inflection in ControllerFactoryFilter.

src/Routing/ScopedRouteCollection.php

@@ -634,8 +634,8 @@ public function merge(ScopedRouteCollection $collection) {
  * @return void
  */
 	public function fallbacks() {
-		$this->connect('/:controller');
-		$this->connect('/:controller/:action/*');
+		$this->connect('/:controller', ['action' => 'index'], ['routeClass' => 'InflectedRoute']);
+		$this->connect('/:controller/:action/*', [], ['routeClass' => 'InflectedRoute']);
 	}
 
 }